Modified tumor cytotoxic factor (TCF) and DNA encoding such

ABSTRACT

Modified TCF in which one or more amino-acid residues of the wild type TCF responsible for glycosylation are substituted or deleted so that at least one N-linked oligosaccharide chain is removed. The modified TCFs have a longer biological half-lives without loss of their biological activities. The modified TCFs are therapeutically important as agents for liver diseases or as anti-cancer drugs.

FIELD OF THE INVENTION

This invention is related to genetically engineered modified TCFs which contain different number of N-linked oligosaccharide chains compared with wild type TCF, and have new amino-acid sequences. These modified TCFs obtained in this invention have longer serum half-lives, have growth stimulating activities for hepatocytes and cytotoxic activities against tumor cells. Therefore, the modified TCFs are useful as therapeutic agents against liver diseases and as anti-cancer drugs.

BACKGROUND OF THE INVENTION

TCF-II, tumor cytotoxic factor derived from human fibroblast, is a novel anti-tumor protein which is different from any other proteins so far reported. The inventors succeeded in cDNA cloning of this protein, deduced its entire amino-acid sequence and confirmed the usefulness. This novel anti-tumor protein and its cDNA were disclosed in W090/10651. They were designated as TCF-II. In this invention, the glycoprotein which has the amino-acid sequence disclosed in W090/10651 is called TCF. TCF is a substance which has been called TCF-II.

TCF has both strong cytotoxic activity against tumor cells and growth stimulating activity for normal cells. And it has been confirmed that TCF is member of a family including HGF, a growth factor for hepatocytes. The. molecular weight of TCF is 78000±2000 daltons and/or 74000±2000 daltons on SDS polyacrylamide gel electrophoresis. Under reducing conditions, it showed a polypeptide band called A chain with a molecular mass of 52000±2000 daltons and two polypeptide bands called B chain and/or C chain with molecular masses of 30000±2000 daltons and/or 26000±2000 daltons, respectively.

Because TCF is a growth factor for hepatocytes, application to liver regeneration after hepatectomy has been examined. Since biological half-life of TCF is very short, attempts have been made to obtain more effective modified TCFs with prolonged biological half-lives.

Relationship between oligosaccharide chains and serum half-lives has been investigated in some glycoproteins including erythropoietin. The investigations have demonstrated that glycoproteins with slightly different structure in oligosaccharide chains and with different biological activities can be synthesized from the same gene. It was known that glycosylated erythropoietin is different in the biological activities from non-glycosylated one. However, about the relationship between oligosaccharide chains and biological activities of TCF little was known.

DISCLOSURE OF THE INVENTION

The present inventors took notice of the usefulness of TCF, and investigated application of TCF to the treatment of tumors or liver diseases and utilization as diagnostic markers of diseases. TCF has a very short half-life of approximately 2 minutes. To obtain modified proteins with prolonged biological half-lives, the inventors constructed several genetically engineered TCFs with mutations in the polypeptide moiety and analyzed them. However, most of the modified proteins appeared to lose the biological activities. Then, to prolong the biological half-life without loss of the biological activity; the inventors paid attention to the four N-linked oligosaccharide chains attached to TCF and attempted to construct the new modified TCFs which have a deletion of one or more oligosaccharide chains.

The theme of this invention is to present the new modified TCFs which have different amino-acid sequences compared to the wild-type TCF, and decreased number of N-linked oligosaccharide chains and longer biological half-lives than the wild-type TCF. These modified TCFs can be obtained by altering the nucleotide sequence of TCF cDNA encoding the amino acid residues responsible for N-glycosylation and by expressing the genetically mutagenized TCF cDNAs. Modified TCFs presented by the invention have one or more deletion(s) of the four N-linked oligosaccharide chains present in the wild-type TCF. These are the first modified TCFs with prolonged biological half lives without any loss of the biological activities, obtained by altering the amino-acid residues of the wild-type TCF.

FIG. 1 shows the entire amino-acid sequence of the wild-type TCF deduced from its cDNA sequence (Seq. Id No. 1). Amino-acid residues responsible for N-glycosylation are underlined. It is speculated that the signal sequence is removed and the glutamine residue at position 32nd results in the N-terminal amino acid of TCF. Four N-linked oligosaccharide chains bind to asparagine residues at positions 258th, 366th, 530th, and 617th relative to the N-terminal amino acid. These asparagine residues correspond to those at positions 89th, 397th, 561st, and 648th in FIG. 1.

FIG. 2 shows cDNA sequence (Seq. Id No. 4) encoding the amino-acid sequence. The coding region starts at the ATG codon marked with a circle in the figure.

Amino-acid residues responsible for N-glycosylation are Asn-X-Thr or Asn-X-Ser (amino-acid residues are indicated by the three-letter code and the X represents any amino-acid residues). Modified TCF lacking specific oligosaccharide chain(s) can be obtained by expressing the nucleotide sequence in which the codons for Asn, Ser or Thr are deleted or substituted with those for one of the other amino acids, in eukaryotic cells, preferably mammalian cells. Modified TCF which lacks specific oligosaccharide chains can be obtained by replacing the codons for Asn with those for other amino acids such as Gln, a substitution with little effects on the conformation of TCF. Gln is the most preferable amino acid which substitutes for Asn. Asp, Glu, His, Ser or Thr are also acceptable. Modified TCF lacking specific oligosaccharide chain(s) can be obtained by replacing the codons for Ser with those for other amino acids such as Ala, a substitution with little effects on the conformation of TCF. Ala is the most preferable amino acid which substitute for Ser. Pro, Gly or Asn are also acceptable. Modified TCF lacking specific oligosaccharide chain(s) can be obtained by deleting or replacing the codons for Thr to other amino acids. Ala is the most preferable amino acid which substitutes for Thr. Val, His or Asn ark also acceptable.

N-glycosylation sites are indicated in a schematic structure of TCF in FIG. 3. The N-glycosylation sites are designated as numbers 1, 2, 3 and 4 from N-terminal. These numbers specify the positions of the N-glycosylation sites.

To alter the amino-acid sequences responsible for N-glycosylation into those for non-glycosylation, the cDNA can be site-specifically mutagenized by PCR(polymerase chain reaction). The reactions are performed by cDNA for the wild-type TCF as the template and synthetic oligonucleotides as the primers. The sequences of primers are designed to delete or substitute the DNA sequences as described above. Other methods for mutagenesis are also applicable.

The cell lines producing the modified TCFs can be established by transforming host cells with expression vectors containing these mutant cDNAs. The modified TCFs can be recovered from the cultured broth of the transformed cell lines.

For example, to substitute Asn at position 289th (FIG. 1), binding site for oligosaccharide chain 1, cDNA was mutagenized by in vitro mutagenesis or mutagenesis by PCR. These mutagenesis reactions are performed by cDNA coding the wild-type TCF disclosed in W0 90/10651 as the template and synthetic oligonucleotide TCF-1R 5'-TCAGTGTCCTGCATAGTAT-3' (Seq. Id No. 5) as the primer. An expression vector containing the mutagenized cDNA can be transferred into eukaryotic cell lines including mammalian cell lines. The modified TCFs can be recovered from the cultured supernatants of the transfected cells.

Any types of host-vector systems for eukaryotic cells are acceptable for expression of the modified TCFs. The most preferable is a combination of cytomegalovirus promoter and Namalwa cells, which was disclosed in W0 92/1053. Commonly used systems including a gene amplification system using a combination of SV 40 promoter, DHFR gene and CHO cell line or an expression system using a combination of the replication origin of bovine papiloma virus and mouse C127 cell line can be enumerated.

Any commonly used methods for purification of biologically active proteins, can be used for purification of the modified TCFs, for example, precipitation by organic solvent, salting out, gel exclusion chromatography, affinity chromatography using monoclonal antibody or electrophoresis. Monoclonal antibodies against the wild-type TCF disclosed in Japanese Patent application number, 3-177236 can be used for affinity chromatography of modified TCF.

The modified TCFs can be stored lyophilized or frozen.

Fifteen modified TCFs can be obtained by combinations of the removal of the oligosaccharide chains. The modified TCFs are identified by numbers removed oligosaccharide chains. For example, the modified TCF which lacks oligosaccharide chain 1 is named TCF-1, the modified TCF which lacks all four oligosaccharide chains is named TCF-1234, and the modified TCF which lacks oligosaccharide chains 2 and 3 is named TCF-23. FIG. 4 schematically represents the N-linked oligosaccharides bound to the modified TCF. All the modified TCFs have different molecular masses according to the removal of oligosaccharide chains.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the entire amino-acid sequence of the wild-type TCF deduced from its cDNA sequence. Amino-acid residues responsible for binding of N-linked oligosaccharide chains are underlined.

FIG. 2 shows the cDNA sequence for the wild-type TCF. Codons to be substituted in the present invention are underlined. The coding sequence starts at the ATG codon marked with a circle.

FIG. 3 schematically represents the primary structure of the wild-type TCF. Circles represent the N-glycosylation sites and the arrow shows the cleavage site between A chain and B chain.

FIG. 4 schematically represents the oligosaccharide chains attached to TCF and the modified TCF. The horizontal lines represent the polypeptides and the vertical bars represents the oligosaccharide chains.

FIG. 5 shows the construction of the plasmids containing cDNAs for the modified TCF.

FIG. 6 shows the construction of the expression vectors for TCF and the modified TCF.

FIG. 7 shows the analysis of the representative modified TCF by SDS polyacrylamide gel electrophoresis.

FIG. 8 shows the stimulating activities of the modified TCF for growth of hepatocytes. Each figure shows the activity of the modified TCF described below.

(1) TCF, TCF-1, TCF-2, TCF-3 and TCF-4

(2) TCF-12, TCF-13, TCF-14, TCF-23, TCF-24 and TCF-34

(3) TCF-123, TCF-124, TCF-1234, TCF-134 and TCF-234

FIG. 9 shows the tumor cytotoxic activities of the modified TCF.

FIG. 10 shows the plasma concentrations of the modified TCF in the rats into which said modified TCFs were intravenously injected.

The novel modified TCFs are obtained by operating the present inventions. The modified TCFs obtained by the present invention can be prepared by expressing the cDNAs in which the codons for the amino-acid residues; responsible for N-glycosylation are substituted with those for other amino acids or are deleted. The modified TCFs have longer biological half-lives due to the control of the numbers and the binding sites of the N-linked oligosaccharide chains.

BEST MODE FOR PRACTICE OF THE INVENTION

In the examples herein, the present invention is described in more detail.

EXAMPLE 1

Preparation of the modified TCFs.

DNAs were manipulated essentially as described in Molecular Cloning, A Laboratory Manual, Second Edition, J. Sambrook, E. F. Fritsch, T. Maniatis, Cold Spring Habor Laboratory Press, New York, 1989 to prepare modified TCFs as described below.

1 Cloning of TCF cDNA.

Site-specific mutations were introduced into TCF cDNA as described below by a 6.3-kb TCF expression plasmid, pcDTCF II, prepared by the method disclosed in W092/01053. The E. coli strain containing pcDTCF II has been deposited to National Institute of Bioscience and Human-Technology as FERM BP-3479.

2 Methods for introducing site-specific mutations.

1) Method 1

i) Cloning of TCF cDNA into M13mp18.

The plasmid pcDTCFII (6.3 kb) was prepared by introducing the entire coding region of human TCF cDNA into plasmid pcDNA I (Invitrogen Co.) digested with restriction enzymes BamHI and SphI (Takara Co.). (/All the restriction enzymes and the modifying enzymes were purchased from Takara Co.) pcDTCFII was digested with BamHI and SphI for 1 hour at 37° C., precipitated with ethanol, and electrophoresed on 1% agarose gel. The 2.3 kb of TCF cDNA fragment was purified from the gel by Gene Clean (Bio101 Co.).

On the other hand, replicative-form of phage DNA, M13mp18 (Takara Co.) as digested with BamHI and SphI, precipitated with ethanol, and dissolved in water to make the vector DNA solution. The vector DNA solution and TCF cDNA were mixed and ligated by the DNA Ligation Kit (Takara Co.). A part of the ligation mixture was used for transformation of E. coli, DH5α. The transformants were mixed with E. coli, NM522, an indicator strain, (Invitrogen Co.) and poured onto the LB soft agar plates containing 1% of bacto-tryptone, 0.5% of bacto-yeast extract, 1% of sodium chloride, 1% of IPTG (isopropyl-β-D-thiogalactoside, Takara Co.), and 1% of Xgal (5-bromo-4-chloro-3-indolyl-β-D-galactoside, Takara Co.) in order to make plaques. The double-stranded phage DNA was prepared from a clear plaque and the single-stranded DNA was prepared and used as a template for introducing site-specific mutations.

ii) Introduction of site-specific mutation.

The codon for the 289th amino acid,/Asn, in a consensus amino acid sequence for N-glycosylation, Asn-X-Thr, was replaced with a codon for Gln that does not make the consensus amino-acid sequence for N-glycosylation.

The definition of the number of amino acid is based on Met at the N-terminal of the wild-type as the first amino acid. The oligonucleotide TCF-1R, 5'-TCAGTGTCCTGCATAGTAT-3' (SEQ ID NO. 5), was synthesized by a DNA synthesizer (Applied Biosystems Co.). All the oligonucleotides were synthesized by the synthesizer unless otherwise noted.

Introduction of site-specific mutation was carried out by the oligonucleotide-directed in vitro mutagenesis system (Amersham Co.) according to the manufacture's instruction. E. coli, NH522 was transformed with the reaction mixture and screened with TCF-1 primer by the plaque hybridization technique.

The single-stranded DNA was prepared from a positive plaque and the sequence was determined by the dideoxy chain termination method described by Sanger et al. to confirm that the codon, AAT, for Asn at 289th, was replaced with the codon, CAG, for Gln. The 1.4-kb PstI-HindIII DNA fragment was prepared from the double-stranded DNA from the positive clone, ligated to PstI-HindIII-digested pBluescript SK+ (Stratagene Co.) to produce plasmid, pSKTCFPH-1.

2) Method 2

Introduction of site-specific mutations in the codons for the 399th, 563rd, and 650th amino acids were carried out essentially as described by R. Higuchi (R. Higuchi, PCR protocols, p.177-183, Academic Press, 1990) using polymerase chain reaction (PCR).A codon for Ser in a consensus amino acid sequence for N-glycosylation, Asn-X-Ser, was replaced with a codon for Ala in each mutagenesis.

To mutagenize the codon for Ser at 399th, 25 cycles of PCR were carried out by a mutant primer, TCF-2R 5'-CCAGATCTTGTTTGAGCTAAGTTGCCC-3' (SEQ ID NO. 6), a wild type primer, TCF701F 5'-GCTGGGATCATCAGACACCAC-3' (SEQ ID NO. 7), AmpliTaq polymerase (Takara Co.), and 4 ng of the plasmid pcDTCF II as a template. The PCR products were purified by centricon 100 (Amicon Co.) to remove primers, digested with restriction enzymes, BglII and EcoRI (Takara Co.), and ligated to the 4.1 kb DNA fragment of BglII-EcoRI-digested pSKTCFPH, plasmid previously produced by ligating PstI-HindIII-digested pBluescript SK+ and 1.4 kb fragment of the Pstl-HindIII-digested pcDTCF II. A part of the ligation mixture was used for transformation of E. coli, DH5α. The plasmid DNAs were prepared from ampicillin resistant transformants and the DNA sequences were determined to screen for plasmid pSKTCFPH-2 in which the codon, TCC, for Ser at 399th was replaced with the codon, GCT, for Ala. Plasmid pSKTCFPH-12 was produced by ligating PCR products and the 4.1 kb DNA fragment of the BglII-EcoRI digested plasmid, pSKTCFPII-1 in a similar way. The DNA sequences of the portion of DNAs derived from PCR products in all plasmids were determined to confirm their sequences. Ampicillin was purchased from Sigma Co.

To mutagenize the codon for Ser at 563rd, 25 cycles of PCR were carried out by a mutant primer, TCF-3R 5'-ATACCAGCTGGGCAACATTGAGAAC-3' (Seq Id No. 8), a wild type primer, TCF1202F 5'-GGCAACTTATCCCAAACAAGATCTGG-3' (SEQ ID NO. 9), AmpliTaq polymerase (Takara Co.), and 4 ng of the plasmid pcDTCF II as a template. The PCR products were purified by centricon 100 (Amicon Co.) to remove primers, digested with restriction enzymes, XhoI and PvuII (Takara Co.). pcDTCF II was digested with XhoI and ligated to generate pcDTCF ΔXho, which lacks the 1.1 kb Xhol DNA fragment. pcDTCF ΔXho was digested with SphI and PvuIl and the 4.8 kb of XhoI-SphI DNA fragment and the 0.5 kb of PvuII-SphI fragment were purified and ligated to XhoI-PvulI-digested PCR products described above by the DNA Ligation Kit. A part of the ligation mixture was used for transformation of E. coli, MC1061/P3 (Invitrogen Co.).

The plasmid DNAs were prepared from ampicillin- and tetracycline-resistant transformants and plasmid, pcDTCF ΔXhoI-3 in which the codon, TCC, for Ser at 563rd was replaced with the codon, GCC, for Ala, was selected in a similar way. Tetracycline was purchased from Sigma Co.

Two rounds of PCR were carried out to mutagenize the codon for Ser at 650th. The first PCRs were carried out independently by AmpliTaq polymerase (Takara Co.), 4 ng of the plasmid pcDTCF II as a template, and a pair of a mutant primer, TCF-4F 5'-ACTCTGAATGAGGCTGAAATATGTG-3' (SEQ ID NO. 10) and a wild type primer, TCF2203R 5'-GGCATGCACAGTTGTATTGGTGGGTGCTTCAG-3' (SEQ ID NO. 11) or a pair of a mutant primer, TCF-4R 5'-CACATATTTCAGCCTCATTCAGAGT-3' (SEQ ID NO. 12) and a wild type primer, TCF1685F 5'-AACAGGTTCTCAATGTTTCCCAG-3'. The PCR products were purified by DE81 paper (Whattman Co.) and one tenth of them was used for the second PCR by the primers, TCF2203R and TCF1685F. The PCR product was separated in an agarose gel, purified by DE81 paper and digested with BglII and SphI. On the other hand, pcDTCFΔXhoI and pcDTCF ΔXhol-3 were digested with BglII and SphI and the 4.9 kb of DNA fragments were purified, ligated to the BglII-SphI-digested PCR fragment described above by the DNA Ligation Kit. One tenth of the ligation mixtures was used to transform E. coli, MC1061/P3. The plasmid DNA were prepared from ampicillin- and tetracycline-resistant transformants and plasmid, pcDTCFΔXhol-4 in which the codon, TCT, for Ser at 650th, was replaced with the codon, GCT, for Ala and plasmid, pcDTCF ΔXhoI-34 in which both codons for Ser at 563rd and at 650th were replaced with the codons for Ala, were selected, in a similar way.

3 Construction of expression vectors.

1) Construction of vectors for transient expression.

Plasmids, pSKTCFPH, pSKTCFPH-1, pSKTCFPH-2, and pSKTCFPH-12were digested with XhoI and 1.1 kb of DNA fragments were purified. Plasmids, pcDTCF ΔXhoI, pcDTCFΔXhoI-3, pcDTCFΔXhol-4, and pcDTCFΔXhoI-34 were digested with XhoI and ligated to four kinds of 1.1 kb of DNA fragments described above. Fifteen ligation mixtures except the combination of 1.1 kb of pSKTCFPH and pcDTCF ΔXhoI were used to transform E. coli, MC1061/P3. Fifteen expression vectors, pcDTCF-1, pcDTCF-2, pcDTCF-3, pcDTCF-4, pcDTCF-12, pcDTCF-13, pcDTCF-14, pcDTCF-23, pcDTCF-24, pcDTCF-34, pcDTCF-123, pcDTCF-124, pcDTCF-134, pcDTCF-234, and pcDTCF-1234were selected. Analysis by restriction enzymes has confirmed the structures of these vectors. When these plasmids are transfected into mammalian cells, for instance COS cells, genes for TCF and the modified TCF are expressed under the control of cytomegalovirus (CMV) promoter. The construction of these plasmids are shown in FIG. 5.

2) Construction of vectors for stable expression.

Plasmid pHSG396 (Takara Co.) was digested with HindIII, blunt-ended with the DNA Blunting Kit (Takara Co.), purified with Gene Clean, ligated to NotI linker, 8 mer 5'-GCGGCCGC-3' (Takara Co.), and used to transform E. coli, DH5α. The plasmid DNAs were prepared from chloramphenicol resistant transformants and plasmid, pHSG NotI, which did not contain HindIll site but contain NotI site was selected. pHSG NotI, was digested with SalI and SphI and ligated to the 2.3 kb of full-length TCF cDNA digested with SalI and SphI to produce plasmid, pHSG N-TCF. The 1.1 kb of XhoI-Xhol fragment was deleted from the plasmid, pHSG N-TCF, to produce plasmid, pHSG N-TCFII ΔX. pHSG N-TCFII ΔX, was digested with BstPI and SphI and the 2.3 kb of DNA fragment was purified, ligated to the BstPI-SphI-digested 15 plasmids, pcDTCF-1, pcDTCF-2, pcDTCF-3, pcDTCF-4, pcDTCF-12, pcDTCF-13, pcDTCF-14,pcDTCF-23, pcDTCF-24, pcDTCF-34, pcDTCF-123, pcDTCF-124, pcDTCF-134,pcDTCF-234, and pcDTCF-1234, and the BstPI-SphI-digested pcDTCF that contained the wild type TCF cDNA by DNA Ligation Kit, and used to transform E. coli, DH5α. The plasmid DNAs were prepared from chloramphenicol-resistant transformants and the 16 plasmids that contained 2.3 kb of the wild-type TCF or each of the mutant TCF cDNAs in the plasmid, pHSG NotI, were selected.

These plasmids were designated as pHSGN-TCF, pHSGN-TCF-1, pHSGN-TCF-2, pHSGN-TCF-3, pHSGN-TCF-4, pHSGN-TCF-12, pHSGN-TCF-13, pHSGN-TCF-14, pHSGN-TCF-23, pHSGN-TCF-24, pHSGN-TCF-34, pHSGN-TCF-123, pHSGN-TCF-124, pHSGN-TCF-134, pHSGN-TCF-234, and pHSGN-TCF-1234. These 16 plasmids were digested with Sall and NotI, ligated to the XhoI-NotI-digested expression vector, BCHGSneo, and used to transform E. coli, DH5α. BCHGSneo is a plasmid that contains the replication origin of bovine papiloma virus and cytomegalovirus promoter, and is capable of replicating in E. coli. BCHGSneo is provided by Dr. H. Karasuyama in Basel Immunology Institute and is described in Idenshikohgaku hand book, p297-299, Yohdo Co., 1991. The plasmid DNAs were prepared from ampicillin resistant transformants and the 16 expression vectors that contained 2.3 kb of wild-type TCF or each of the mutant TCF cDNAs in BCHGSneo were selected. These plasmids were designated as, pBPV-TCF, pBPV-TCF-1, pBPV-TCF-2, pBPV-TCF-3, pBPV-TCF-4, pBPV-TCF-12, pBPV-TCF-13, pBPV-TCF-14, pBPV-TCF-23, pBPV-TCF-24, pBPV-TCF-34, pBPV-TCF-123, pBPV-TCF-124, pBPV-TCF-134, pBPV-TCF-234, and pBPV-TCF-1234. Antibiotics, chloramphenicol was purchased from Sigma Co. E. coli strains containing pBPV-TCF-3 or pBPV-TCF-13 were deposited to National Institute of Bioscience and Human Technology as FERM BP-4454 and FERM BP-4455.

4 Preparation and purification of the TCF or the modified TCFs expression plasmids.

The 16 E. coli strains containing each of the expression vectors, pBPV-TCF, pBPV-TCF-1, pBPV-TCF-2, pBPV-TCF-3, pBPV-TCF-4, pBPV-TCF-12, pBPV-TCF-13, pBPV-TCF-14, pBPV-TCF-23, pBPV-TCF-24, pBPV-TCF-34, pBPV-TCF-123, pBPV-TCF-124, pBPV-TCF-134, pBPV-TCF-234, and pBPV-TCF-1234, were cultured in 400 ml of medium containing 50 μg/ml of ampicillin at 37° C. When the absorbance at 600 nm of each culture broth reached 0.8, chloramphenicol was added to the broth at a final concentration of 170 μg/ml and each broth was cultured overnight. These 16 plasmids were prepared by the alkali-SDS method and purified by cesium chloride density gradient ultra centrifugation as described by Maniatis et. al. (Molecular Cloning 2nd ed.).

5 Transfection of the TCF- and the modified TCF- expression plasmids into the cultured animal cell lines.

The 16 expression plasmids were transfected into a mouse cell line, C 127 by TRANSFECTM (IBF Co. Maryland, USA), DNA transfection reagent for cultured mammalian cell lines, as described below. One day prior to transfection, approximately 10⁶ cells of mouse C127 were suspended in DME medium (GIBCO Co.) containing 10% of fetal calf serum and incubated at 37° C. overnight in a CO₂ incubator (a humidified incubator in an atmosphere of 5-7% of CO₂), in 25 cm² tissue culture flasks (Sumitomo Bakelite, for adherent cells). (Cells were cultured at 37° C. in a humidified incubator in an atmosphere of 5-7% CO₂, unless otherwise noted.). The cells were washed twice with Opti. MEM medium (GIBCO Co.) before transfection. After adding 2 ml of Opti. MEM to the monolayer of the cells, transfection was carried out by 10 μg of the plasmid DNA as described in the manufacturer's protocol. After incubated for 6 hours, 7.5 ml of DME medium was added to the flasks. Then, the cells were incubated for two more days at 37° C. The medium was replaced with fresh DME medium on the first day. The cells were trypsinized, washed once with DME medium and suspended in 50 mL of DME medium containing 100 μg/ml of G418. One hundred micro-liter of the suspension was added to each well in a 96-well flat-bottomed plates and incubated at 37° C. One week later, 100 μL of DME medium containing 100 μg/ml of G418 was added to each well, and the plates were incubated at 37° C. Another week later, expression of the TCF or the modified TCFs was detected by measuring the concentration of TCF or the modified TCFs in 100 μL of the cultured media by an enzyme immuno assay employing anti-TCF monoclonal antibodies (N. Shima et. al. Gastroenterologia Japonica 26 (4) 477-482, 1991). The cell lines expressing TCF or the modified TCFs were cultured at 37° C. in a 12-well tissue culture plate or in a 25 cm² flask according to the cell numbers. Cell lines which express the modified TCFs (a total of 15 modified TCFs designated as TCF-1, TCF-2, TCF-3, TCF-4, TCF-12, TCF-13, TCF-14, TCF-23, TCF-24, TCF-34, TCF-123, TCF-124, TCF-134, TCF-234, and TCF-1234) were thus obtained.

6 Large-scale cultivation of the cell lines which produce TCF or the modified TCFs.

The confluent cells producing TCF or the modified TCFs in 75 cm² tissue culture flasks were harvested by trypsinization, followed by inoculating into three 225 cm² tissue culture flasks. One hundred milliliters of DME medium was added to each flask and the culture was incubated at 37° C. Four days later, the confluent cells were trypsinized and suspended in the DME medium. The cell suspension was diluted 10-fold with DME medium (a total volume of 3 L). One hundred milliliters of the diluted cell suspension was inoculated into a new 225 cm² tissue culture flask. The cells were cultured at 37° C. for 5 days in thirty 225 cm² tissue culture flasks. The cultured supernatant (a total volume of 3 L) was collected. Cells were harvested from 6 flasks, followed by inoculating into sixty 225 cm² tissue culture flasks. To each flask, 100 ml of the medium was added and incubated at 37° C. for 5 days. The cultured supernatant (a total volume of 6 L) was collected. Thus, 9 L of the cultured supernatant which contains the TCF or the modified TCFs was obtained.

7 Purification of the TCF and the modified TCFs.

A three-step purification was performed as described below.

1) Heparin-sepharose CL-6B

Nine liters of the cultured supernatant which contains each of the modified TCF was centrifuged at 6,000 rpm for 30 min. to remove insoluble materials. The supernatant was applied at an approximate flow rate of 200 ml per hour to a heparin-sepharose CL-6B column (2.5×12 cm) (Pharmacia Co.) which had been equilibrated with 300 mL of the equilibration buffer,10 mM Tris-HCl buffer (pH 7.5) containing 0.5M of NaCl and 0.01% of Tween 20. The column was then washed with approximately 700 mL of the equilibration buffer. The TCF or the modified TCFs were eluted with 10 mM Tris-HCl buffer (pH 7.5) containing 2M NaCl and 0.01% of Tween 20 and the fractions of 3 mL were collected. The fractions were monitored by the absorbance at 280 nm and the fractions containing TCF or the modified TCFs (approximately 100 mL) were obtained.

2l) Mono S-FPLC

The eluate which contains TCF or the modified TCFs was dialyzed against 10 mM of phosphate buffer (pH 6.5) containing 0.15M of NaCl and centrifuged at 12,000 rpm for 90 min. to remove insoluble materials. The supernatant was applied at a flow rate of 1 mL/min. to a Mono S column (0.5×5 cm, Pharmacia, FPLC) which had been equilibrated with approximately 20 ml of 10 mM phosphate buffer (pH 7.0) containing 0.15M NaCl and 0.01% Tween 20 (buffer A). The column was washed once with approximately 30 mL of buffer A. Then the TCF or the modified TCFs were eluted at a flow rate of 0.5 mL/min. from the column with a linear gradient of NaCl (up to 1.0M) and fractions of 0.5 ml were collected. The fractions containing TCF or the modified TCFs (an approximate volume of 4 mL) which were eluted with 0.7-0.8M NaCl were obtained.

3) Heparin 5-PW-FPLC

Two volumes (8 mL)of 10 mM Tris-HCl (pH 7.5) containing 0.01% Tween 20 were added to the eluate which contains TCF or the modified TCFs. This diluted solution was applied at a flow rate of 1 mL/min. to a heparin 5-PW column (0.5×7.5 cm, TOSO Co., FPLC) which had been equilibrated with approximately 20 mL of 10 mM Tris-HCl buffer (pH 7.5) containing 0.3M NaCl and 0.01% Tween 20 (buffer B). The column was washed with approximately 30 ml of buffer B. Then TCF or the modified TCFs were eluted at a flow rate of 0.5 mL/min. with a linear gradient of NaCl (up to 2.0M) and fractions of 0.5 ml were collected. The fractions containing TCF or the modified TCFs (those eluted with approximately 1.3M NaCl, a total volume of 3 mL) were obtained. These fractions were dialyzed against deionized water, lyophilized and reconstituted with phosphate-buffered saline (PBS) containing 0.001% Tween 20. The yield and the recovery of each of the final purified modified TCFs are shown in Table 1. The yields were determined with polyclonal EIA described in the following section.

                  TABLE 1                                                          ______________________________________                                         The yield and the recovery of each of the final purified modified TCFs         Name           Yield(μg)                                                                            Recovery(%)                                            ______________________________________                                         TCF            2760     31                                                     TCF-1          872      17                                                     TCF-2          920      40                                                     TCF-3          253      16                                                     TCF-4          560      16                                                     TCF-12         688      33                                                     TCF-13         1088     23                                                     TCF-14         350      27                                                     TCF-23         810      28                                                     TCF-24         648      19                                                     TCF-34         668      34                                                     TCF-123        340      11                                                     TCF-124        400      23                                                     TCF-134        187      22                                                     TCF-234        400      15                                                     TCF-1234       155       8                                                     ______________________________________                                    

8 Quantitation of the purified modified TCFs.

1) Preparation of polyclonal antibodies and labeling of the antibodies.

Anti-TCF antiserum was obtained from rabbits which were immunized with TCF. The anti-TCF lgG was purified from the antiserum by an Affi-Gel protein A Sepharose (Bio Rad Co.) according to the manufacturer's protocol. The purified IgG was dialyzed overnight against PBS, and applied at a flow rate of 0.5 mL/min. to a TCF affinity column in which TCF was immobilized to affigel 10 (Bio Rad Co.). The immobilized column was washed with PBS and the anti-TCF IgG was eluted with 0.1M Glycine-HCl buffer (pH 2.5). The eluate was dialyzed against PBS and the purified anti-TCF polyclonal antibodies were thus obtained. The peroxydase labeled antibodies were prepared as described by Ishikawa et al. (J. Immunoassay, vol. 4, 209-327, 1983).

2) Quantitation of the purified modified TCFs.

Anti-TCF antibodies were dissolved at a concentration of 10 μg/mL in 0.1M NaHCO₃. The antibody solution was added (100 μL/well) to 96-well microtiter plates (NUNC Co.) and left overnight at room temperature. This step allowed the antibodies to attach to the plates. Block Ace (Snow Brand Milk Products Co. Ltd.) diluted two-fold with deionized water was added to the antibody-coated microtiter-well plates (200 μL/ml) and left for an hour at room temperature for blocking each well. The plates were then washed three times with PBS containing 0.1% Tween 20 (washing buffer). The modified TCF were diluted with appropriate volume of the first buffer (0.2M Tris-HCl pH 7.4 containing 40% Block Ace and 0.1% Tween 20) to prepare modified TCF samples. Standard TCF solution was prepared by sequentially diluting 10 ng/mL of TCF solution with the first buffer. One hundred micro liters of the modified TCF samples were added to each well, left for 3 hours at 37° C. and washed three times with the washing buffer. The Peroxydase-conjugated antibody solution was diluted 400-fold with the second buffer (0.1M Tris-HCl buffer pH 7.4 containing 20% Block Ace, 0.1% Tween 20 and 0.5 mg/mL of mouse IgG). One hundred microliters of the diluted peroxydase-labeled antibody solution was added to each well, left for 2 hours at 37° C. and washed three times with the washing buffer. Subsequently, 100 μL of substrate solution (0.4 mg/mL of o-phenylene diamine dihydrochloride and 0.006% H₂ O₂ in 0.1M citrate-phosphate buffer, pH 4.5) was added to each well and incubated at 37° C. for 30 minutes in a dark place. The enzyme reaction was stopped by addition of 50 μL of 6N H₂ SO₄. The absorbance at 492 nm was measured on an immuno reader (Corona Co.).

9 Analysis of the purified TCF or the modified TCFs on SDS-polyacrylamide gel electrophoresis.

Five micrograms of purified modified TCF was subjected to an SDS-polyacrylamide gel. Modified TCFs (TCF-3 and TCF-13) with prolonged biological half-lives as described later, and the wild-type TCF were applied to an SDS-polyacrylamide gel electrophoresis. The results are shown in FIG. 7. Electrophoresis was performed either in the presence (reducing conditions) or absence (non-reducing conditions) of β-mercaptoethanol. As indicated in FIG. 7 TCF showed two adjacent bands with approximate molecular masses of 78,000 and 74,000 under non-reducing conditions. The two bands of TCF-3 migrated faster than those of TCF, and the two bands of TCF-13 migrated faster than those of TCF-3, under non-reducing conditions. Under the reducing conditions, three protein bands with approximate molecular masses of 52,000, 30,000 and 26,000 were observed for TCF. Similarly, three bands with 52,000, 26,000 and 22,000 for TCF-3, and three bands with 48,000, 26,000 and 22,000 for TCF-13 were observed. The decrease in molecular mass of these modified TCFs was probably due to the removal of oligosaccharide chains. The results suggested that the desired modified TCFs were obtained. No other protein bands were detected except those deduced from the structure of the two modified proteins.

EXAMPLE 2

Biological activities of the TCF and the modified TCFs in vitro.

1 Growth stimulating activity for hepatocytes.

Growth stimulating activity for hepatocytes was determined as follows. Rat hepatocytes were isolated from a Wister rat (body weight was approximately 200 g) by the method of Seglen (Methods in cell biology Vol.13, p.29, Academic, Press, New York). The basal medium, Williams E (Flow laboratories Co.), containing 10% fetal bovine serum and 10 μM dexamethasone) was used for the growth of the cells. One hundred microliters of the basal medium containing 1.0×10⁴ cells was added to each well in a 96-well flat-bottomed plate (Falcon Co.) and incubated at 37° C. after 24 hours of incubation, 100 μL of the basal medium containing TCF or the modified TCFs was added to each well and incubated for 22 hours at 37° C. Each well was supplemented with 1 μCi of ³ H-thimidine (Amersham Co.) and further incubated at 37° C. for 2 hours. After washing twice with cold PBS, cells were trypsinized with 0.5% trypsine and harvested on a sheet of glass filter by a cell harvester. Radioactivities incorporated into the cells in each well were counted by Matrix 96 (Packard Co.). As shown in FIG. 8, all the modified TCFs were shown to maintain growth stimulating activities for rat hepatocytes.

2 Tumor cytotoxic activity.

Tumor cytotoxic activities of TCF, TCF-3 and TCF-13 were measured. Meth A sarcoma was used as a target cell line. The cells were suspended in RPMI medium (GIBCO Co.) supplemented with 10% FCS at a final cell density of 2×10⁴ cells per mL. Fifty microliters of the cell suspension was inoculated into each well in 96-well flat-bottomed microtiter plates. The purified TCF, TCF-3 and TCF-13 were serially diluted with RPMI medium from the concentration of 50 ng/mL, and the 50 μL of each diluted sample was added to each test well. After incubation at 37° C. for 5 days, MTT was added at a final concentration of 0.5 mg/ml and the plates were incubated at 37° C. Four hours later, 100 μL of the solution containing 10% SDS and 0.01M NH₄ Cl was added to each well and left overnight at room temperature. Next day, the absorbance at 620 nm was measured as a parameter of the viable cell numbers in each well. FIG. 9 shows the results of the assay. TCF, TCF-3 and TCF-13 having cytotoxic activities to Meth A cells in a dose-dependent manner.

EXAMPLE 3

Measurement of biological half-lives of the TCF and the modified TCFs in vivo.

Anti-TCF polyclonal antibody was dissolved in 0.1M NaHCO₃ solution to a final concentration of 10 μg/mL. One hundred microliters of the antibody solution was added to each well and the plates were left overnight at room temperature. The wells were filled with 50% solution of Block Ace in H₂ O, incubated for 1 hour at room temperature and washed three times with washing solution (PBS containing 0.1% Tween 20 ). Plasma samples periodically collected from the rats which were intravenously injected with TCF or the modified TCFs were diluted with normal rat serum, when necessary. TCF solutions serially diluted with normal rat serum (from 10 ng/mL) was used as the standard TCF solution. Fifty microliters of the sample solution and 50 μL of the first buffer (0.2M Tris HCl pH 7.3 containing 50% Block Ace, 0.2M NaCl, 0.1% Tween 20, 0.2% CHAPS, 20 mM Benzamidine hydrochloride, and 10 mM EDTA) was mixed and added to each well. The plates were left for 3 hours at 37° C. and washed three times with the washing buffer. One hundred microliters of the peroxidase-labeled anti-TCF antibody solution, which was 400-fold diluted with 0.1M phosphate buffer pH 7.0 containing 10% Block Ace, 0.15M NaCl, 0.1% Tween 20, 4% rat serum and 0.5% mouse IgG, was added to each well. Plates were incubated for hours at 37° C. and washed three times with the washing buffer. Subsequently, 100 μL of substrate solution (0.4 mg/mL of o-phenylene diamine dihydrochloride and 0.006% H₂ O₂ in 0.1M citrate-phosphate buffer, pH 4.5) was added to each well and incubated at 37° C. for 30 minutes in a dark place. The enzyme reaction was stopped by addition of 50 μL of 6N H₂ SO₄. The absorbance at 492 nm was measured on an immuno reader (Corona Co.). Thus concentrations of the TCF or the modified TCFs in rat serum were determined.

Time course of plasma levels were examined by EIA in rats after the single intravenous injection of TCF and the modified TCFs. Hale Wister rats weighing about 200 g were used. After the intravenous injection of TCF to the rats, the plasma level declined biexponentially, well described by a two-compartment model. Plasma half-lives of rapid phase and slower phase were 2.4±2.5 min.(t1/2β) and 15.6±4.6 min.(t1/2β) in rats after the TCF injection at a dose of 50 μg/kg, respectively. Plasma level profiles of modified TCF were similar to that of the wild-type TCF, but their plasma levels declined slower than that of the wild-type TCF after the intravenous injection at the same dose.

As shown in Table 2, plasma half-lives of TCF-3 and TCF-13 were prolonged and their total clearance was decreased. TCF-3 and TCF-13 had larger AUC(the area under the plasma concentration--time curve) compared to the wild-type TCF.

                  TABLE 2                                                          ______________________________________                                         Pharmacokinetics parameters of the modified TCFs                                            t.sub.1/2  α                                                                        t.sub.1/2  β                                      SAMPLE       (min)      (min)                                                  ______________________________________                                         TCF          2.4 ± 0.5                                                                              15.6 ± 4.6                                          TCF-1        2.4 ± 0.3                                                                              19.6 ± 0.3                                          TCF-2        2.2 ± 0.6                                                                              18.2 ± 2.5                                          TCF-3        2.9 ± 0.3                                                                               54.2 ± 8.3**                                       TCF-4        2.7 ± 0.1                                                                              20.6 ± 3.3                                          TCF-12       2.7 ± 0.3                                                                              18.1 ± 1.6                                          TCF-13        3.8 ± 0.5**                                                                            24.9 ± 3.1*                                        TCF-14       1.9 ± 0.4                                                                              18.8 ± 2.9                                          TCF-23       2.4 ± 0.5                                                                              15.4 ± 0.5                                          TCF-24       2.3 ± 0.1                                                                              16.9 ± 1.7                                          TCF-34       2.2 ± 0.5                                                                              18.0 ± 2.1                                          TCF-123      2.2 ± 0.1                                                                              17.2 ± 0.8                                          TCF-124      2.3 ± 0.1                                                                              15.7 ± 2.7                                          TCF-134      2.3 ± 0.4                                                                              19.1 ± 3.2                                          TCF-234      2.6 ± 0.6                                                                              16.8 ± 1.6                                          TCF-1234      2.9 ± 0.1*                                                                             24.2 ± 5.5*                                        ______________________________________                                          Mean ± SD                                                                   Significantly difference from Wildtype TCF (*P < 0.05, **P < 0.01)       

                  TABLE 3                                                          ______________________________________                                         Pharmacokinetics parameters of the modified TCFs                                           AUC          CL.sub.total                                          SAMPLE      (ng · min/ml)                                                                      (ml/min/kg)                                           ______________________________________                                         TCF         1030.0 ± 257.9                                                                            51.5 ± 13.9                                       TCF-1        811.6 ± 158.3                                                                            63.2 ± 12.2                                       TCF-2       1143.7 ± 551.7                                                                            49.8 ± 18.9                                       TCF-3          2679 ± 292.1**                                                                         18.8 ± 2.1**                                      TCF-4        897.8 ± 263.5                                                                            58.6 ± 14.7                                       TCF-12      1246.4 ± 290.8                                                                            41.7 ± 10.6                                       TCF-13       8301.0 ± 299.7**                                                                          6.0 ± 0.2**                                      TCF-14       972.5 ± 162.2                                                                           52.5 ± 9.5                                         TCF-23      1223.0 ± 356.7                                                                            43.6 ± 14.3                                       TCF-24      1017.8 ± 210.0                                                                           51.0 ± 8.3                                         TCF-34      983.0 ± 61.0                                                                             51.0 ± 3.2                                         TCF-123     963.8 ± 66.2                                                                             52.0 ± 3.5                                         TCF-124     1126.3 ± 265.0                                                                           45.9 ± 9.5                                         TCF-134      960.9 ± 279.7                                                                            55.2 ± 16.7                                       TCF-234      892.9 ± 119.7                                                                           56.6 ± 7.1                                         TCF-1234    1266.5 ± 78.9                                                                            39.6 ± 2.6                                         ______________________________________                                          Mean ± SD                                                                   Significantly difference from Wildtype TCF (*P < 0.05, **P < 0.01)       

These results indicated that TCF-3 and TCF-13 had slower metabolic fates and have larger bioavailabilities than those of the wild-type TCF. The amino acid sequence of TCF-3 discloses in Seq Id No. 2, and the sequence of TCF-13 discloses in Seq Id No. 3.

The modified TCFs in the present invention have longer biological half-lives, maintaining growth stimulating activities for hepatocytes and cytotoxic activities to tumor cells, and are therefore useful as therapeutic agents for liver diseases or as anti-cancer drugs.

REFERENCE OF MICROORGANISM

(1) pcTCF(S)/MC1061/P3

Organization of Deposition:

National Institute of Bioscience and Human-Technology,

Agency of Industrial Science and Technology,

Ministry of International Trade and Industry

Address:

1-3, Higashi 1 chome, Tsukuba-shi, Ibaraki-ken, Japan

Deposition Number:

FERM BP-3479

(2) pBPV-TCF-3

Organization of Deposition:

National Institute of Bioscience and Human-Technology,

Agency of Industrial Science and Technology,

Ministry of International Trade and Industry

Address:

1-3, Higashi 1 chome, Tsukuba-shi, Ibaraki-ken, Japan

Deposition Number:

FERM BP-4454

(3) pBPV-TCF-13

Organization of Deposition:

National Institute of Bioscience and Human-Technology,

Agency of Industrial Science and Technology,

Ministry of International Trade and Industry

Address:

1-3, Higashi 1 chome, Tsukuba-shi, Ibaraki-ken, Japan

Deposition Number:

FERM BP-4455

    __________________________________________________________________________     SEQUENCE LISTING                                                               (1) GENERAL INFORMATION:                                                       (iii) NUMBER OF SEQUENCES: 13                                                  (2) INFORMATION FOR SEQ ID NO:1:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 723 amino acids                                                    (B) TYPE: amino acid                                                           (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                        MetTrpValThrLysLeuLeuProAlaLeuLeuLeuGlnHisValLeu                               151015                                                                         LeuHisLeuLeuLeuLeuProIleAlaIleProTyrAlaGluGlyGln                               202530                                                                         ArgLysArgArgAsnThrIleHisGluPheLysLysSerAlaLysThr                               354045                                                                         ThrLeuIleLysIleAspProAlaLeuLysIleLysThrLysLysVal                               505560                                                                         AsnThrAlaAspGlnCysAlaAsnArgCysThrArgAsnLysGlyLeu                               65707580                                                                       ProPheThrCysLysAlaPheValPheAspLysAlaArgLysGlnCys                               859095                                                                         LeuTrpPheProPheAsnSerMetSerSerGlyValLysLysGluPhe                               100105110                                                                      GlyHisGluPheAspLeuTyrGluAsnLysAspTyrIleArgAsnCys                               115120125                                                                      IleIleGlyLysGlyArgSerTyrLysGlyThrValSerIleThrLys                               130135140                                                                      SerGlyIleLysCysGlnProTrpSerSerMetIleProHisGluHis                               145150155160                                                                   SerTyrArgGlyLysAspLeuGlnGluAsnTyrCysArgAsnProArg                               165170175                                                                      GlyGluGluGlyGlyProTrpCysPheThrSerAsnProGluValArg                               180185190                                                                      TyrGluValCysAspIleProGlnCysSerGluValGluCysMetThr                               195200205                                                                      CysAsnGlyGluSerTyrArgGlyLeuMetAspHisThrGluSerGly                               210215220                                                                      LysIleCysGlnArgTrpAspHisGlnThrProHisArgHisLysPhe                               225230235240                                                                   LeuProGluArgTyrProAspLysGlyPheAspAspAsnTyrCysArg                               245250255                                                                      AsnProAspGlyGlnProArgProTrpCysTyrThrLeuAspProHis                               260265270                                                                      ThrArgTrpGluTyrCysAlaIleLysThrCysAlaAspAsnThrMet                               275280285                                                                      AsnAspThrAspValProLeuGluThrThrGluCysIleGlnGlyGln                               290295300                                                                      GlyGluGlyTyrArgGlyThrValAsnThrIleTrpAsnGlyIlePro                               305310315320                                                                   CysGlnArgTrpAspSerGlnTyrProHisGluHisAspMetThrPro                               325330335                                                                      GluAsnPheLysCysLysAspLeuArgGluAsnTyrCysArgAsnPro                               340345350                                                                      AspGlySerGluSerProTrpCysPheThrThrAspProAsnIleArg                               355360365                                                                      ValGlyTyrCysSerGlnIleProAsnCysAspMetSerHisGlyGln                               370375380                                                                      AspCysTyrArgGlyAsnGlyLysAsnTyrMetGlyAsnLeuSerGln                               385390395400                                                                   ThrArgSerGlyLeuThrCysSerMetTrpAspLysAsnMetGluAsp                               405410415                                                                      LeuHisArgHisIlePheTrpGluProAspAlaSerLysLeuAsnGlu                               420425430                                                                      AsnTyrCysArgAsnProAspAspAspAlaHisGlyProTrpCysTyr                               435440445                                                                      ThrGlyAsnProLeuIleProTrpAspTyrCysProIleSerArgCys                               450455460                                                                      GluGlyAspThrThrProThrIleValAsnLeuAspHisProValIle                               465470475480                                                                   SerCysAlaLysThrLysGlnLeuArgValValAsnGlyIleProThr                               485490495                                                                      ArgThrAsnIleGlyTrpMetValSerLeuArgTyrArgAsnLysHis                               500505510                                                                      IleCysGlyGlySerLeuIleLysGluSerTrpValLeuThrAlaArg                               515520525                                                                      GlnCysPheProSerArgAspLeuLysAspTyrGluAlaTrpLeuGly                               530535540                                                                      IleHisAspValHisGlyArgGlyAspGluLysCysLysGlnValLeu                               545550555560                                                                   AsnValSerGlnLeuValTyrGlyProGluGlySerAspLeuValLeu                               565570575                                                                      MetLysLeuAlaArgProAlaValLeuAspAspPheValSerThrIle                               580585590                                                                      AspLeuProAsnTyrGlyCysThrIleProGluLysThrSerCysSer                               595600605                                                                      ValTyrGlyTrpGlyTyrThrGlyLeuIleAsnTyrAspGlyLeuLeu                               610615620                                                                      ArgValAlaHisLeuTyrIleMetGlyAsnGluLysCysSerGlnHis                               625630635640                                                                   HisArgGlyLysValThrLeuAsnGluSerGluIleCysAlaGlyAla                               645650655                                                                      GluLysIleGlySerGlyProCysGluGlyAspTyrGlyGlyProLeu                               660665670                                                                      ValCysGluGlnHisLysMetArgMetValLeuGlyValIleValPro                               675680685                                                                      GlyArgGlyCysAlaIleProAsnArgProGlyIlePheValArgVal                               690695700                                                                      AlaTyrTyrAlaLysTrpIleHisLysIleIleLeuThrTyrLysVal                               705710715720                                                                   ProGlnSer                                                                      (2) INFORMATION FOR SEQ ID NO:2:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 723 amino acids                                                    (B) TYPE: amino acid                                                           (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                        MetTrpValThrLysLeuLeuProAlaLeuLeuLeuGlnHisValLeu                               151015                                                                         LeuHisLeuLeuLeuLeuProIleAlaIleProTyrAlaGluGlyGln                               202530                                                                         ArgLysArgArgAsnThrIleHisGluPheLysLysSerAlaLysThr                               354045                                                                         ThrLeuIleLysIleAspProAlaLeuLysIleLysThrLysLysVal                               505560                                                                         AsnThrAlaAspGlnCysAlaAsnArgCysThrArgAsnLysGlyLeu                               65707580                                                                       ProPheThrCysLysAlaPheValPheAspLysAlaArgLysGlnCys                               859095                                                                         LeuTrpPheProPheAsnSerMetSerSerGlyValLysLysGluPhe                               100105110                                                                      GlyHisGluPheAspLeuTyrGluAsnLysAspTyrIleArgAsnCys                               115120125                                                                      IleIleGlyLysGlyArgSerTyrLysGlyThrValSerIleThrLys                               130135140                                                                      SerGlyIleLysCysGlnProTrpSerSerMetIleProHisGluHis                               145150155160                                                                   SerTyrArgGlyLysAspLeuGlnGluAsnTyrCysArgAsnProArg                               165170175                                                                      GlyGluGluGlyGlyProTrpCysPheThrSerAsnProGluValArg                               180185190                                                                      TyrGluValCysAspIleProGlnCysSerGluValGluCysMetThr                               195200205                                                                      CysAsnGlyGluSerTyrArgGlyLeuMetAspHisThrGluSerGly                               210215220                                                                      LysIleCysGlnArgTrpAspHisGlnThrProHisArgHisLysPhe                               225230235240                                                                   LeuProGluArgTyrProAspLysGlyPheAspAspAsnTyrCysArg                               245250255                                                                      AsnProAspGlyGlnProArgProTrpCysTyrThrLeuAspProHis                               260265270                                                                      ThrArgTrpGluTyrCysAlaIleLysThrCysAlaAspAsnThrMet                               275280285                                                                      AsnAspThrAspValProLeuGluThrThrGluCysIleGlnGlyGln                               290295300                                                                      GlyGluGlyTyrArgGlyThrValAsnThrIleTrpAsnGlyIlePro                               305310315320                                                                   CysGlnArgTrpAspSerGlnTyrProHisGluHisAspMetThrPro                               325330335                                                                      GluAsnPheLysCysLysAspLeuArgGluAsnTyrCysArgAsnPro                               340345350                                                                      AspGlySerGluSerProTrpCysPheThrThrAspProAsnIleArg                               355360365                                                                      ValGlyTyrCysSerGlnIleProAsnCysAspMetSerHisGlyGln                               370375380                                                                      AspCysTyrArgGlyAsnGlyLysAsnTyrMetGlyAsnLeuSerGln                               385390395400                                                                   ThrArgSerGlyLeuThrCysSerMetTrpAspLysAsnMetGluAsp                               405410415                                                                      LeuHisArgHisIlePheTrpGluProAspAlaSerLysLeuAsnGlu                               420425430                                                                      AsnTyrCysArgAsnProAspAspAspAlaHisGlyProTrpCysTyr                               435440445                                                                      ThrGlyAsnProLeuIleProTrpAspTyrCysProIleSerArgCys                               450455460                                                                      GluGlyAspThrThrProThrIleValAsnLeuAspHisProValIle                               465470475480                                                                   SerCysAlaLysThrLysGlnLeuArgValValAsnGlyIleProThr                               485490495                                                                      ArgThrAsnIleGlyTrpMetValSerLeuArgTyrArgAsnLysHis                               500505510                                                                      IleCysGlyGlySerLeuIleLysGluSerTrpValLeuThrAlaArg                               515520525                                                                      GlnCysPheProSerArgAspLeuLysAspTyrGluAlaTrpLeuGly                               530535540                                                                      IleHisAspValHisGlyArgGlyAspGluLysCysLysGlnValLeu                               545550555560                                                                   AsnValAlaGlnLeuValTyrGlyProGluGlySerAspLeuValLeu                               565570575                                                                      MetLysLeuAlaArgProAlaValLeuAspAspPheValSerThrIle                               580585590                                                                      AspLeuProAsnTyrGlyCysThrIleProGluLysThrSerCysSer                               595600605                                                                      ValTyrGlyTrpGlyTyrThrGlyLeuIleAsnTyrAspGlyLeuLeu                               610615620                                                                      ArgValAlaHisLeuTyrIleMetGlyAsnGluLysCysSerGlnHis                               625630635640                                                                   HisArgGlyLysValThrLeuAsnGluSerGluIleCysAlaGlyAla                               645650655                                                                      GluLysIleGlySerGlyProCysGluGlyAspTyrGlyGlyProLeu                               660665670                                                                      ValCysGluGlnHisLysMetArgMetValLeuGlyValIleValPro                               675680685                                                                      GlyArgGlyCysAlaIleProAsnArgProGlyIlePheValArgVal                               690695700                                                                      AlaTyrTyrAlaLysTrpIleHisLysIleIleLeuThrTyrLysVal                               705710715720                                                                   ProGlnSer                                                                      (2) INFORMATION FOR SEQ ID NO:3:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 723 amino acids                                                    (B) TYPE: amino acid                                                           (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                        MetTrpValThrLysLeuLeuProAlaLeuLeuLeuGlnHisValLeu                               151015                                                                         LeuHisLeuLeuLeuLeuProIleAlaIleProTyrAlaGluGlyGln                               202530                                                                         ArgLysArgArgAsnThrIleHisGluPheLysLysSerAlaLysThr                               354045                                                                         ThrLeuIleLysIleAspProAlaLeuLysIleLysThrLysLysVal                               505560                                                                         AsnThrAlaAspGlnCysAlaAsnArgCysThrArgAsnLysGlyLeu                               65707580                                                                       ProPheThrCysLysAlaPheValPheAspLysAlaArgLysGlnCys                               859095                                                                         LeuTrpPheProPheAsnSerMetSerSerGlyValLysLysGluPhe                               100105110                                                                      GlyHisGluPheAspLeuTyrGluAsnLysAspTyrIleArgAsnCys                               115120125                                                                      IleIleGlyLysGlyArgSerTyrLysGlyThrValSerIleThrLys                               130135140                                                                      SerGlyIleLysCysGlnProTrpSerSerMetIleProHisGluHis                               145150155160                                                                   SerTyrArgGlyLysAspLeuGlnGluAsnTyrCysArgAsnProArg                               165170175                                                                      GlyGluGluGlyGlyProTrpCysPheThrSerAsnProGluValArg                               180185190                                                                      TyrGluValCysAspIleProGlnCysSerGluValGluCysMetThr                               195200205                                                                      CysAsnGlyGluSerTyrArgGlyLeuMetAspHisThrGluSerGly                               210215220                                                                      LysIleCysGlnArgTrpAspHisGlnThrProHisArgHisLysPhe                               225230235240                                                                   LeuProGluArgTyrProAspLysGlyPheAspAspAsnTyrCysArg                               245250255                                                                      AsnProAspGlyGlnProArgProTrpCysTyrThrLeuAspProHis                               260265270                                                                      ThrArgTrpGluTyrCysAlaIleLysThrCysAlaAspAsnThrMet                               275280285                                                                      GlnAspThrAspValProLeuGluThrThrGluCysIleGlnGlyGln                               290295300                                                                      GlyGluGlyTyrArgGlyThrValAsnThrIleTrpAsnGlyIlePro                               305310315320                                                                   CysGlnArgTrpAspSerGlnTyrProHisGluHisAspMetThrPro                               325330335                                                                      GluAsnPheLysCysLysAspLeuArgGluAsnTyrCysArgAsnPro                               340345350                                                                      AspGlySerGluSerProTrpCysPheThrThrAspProAsnIleArg                               355360365                                                                      ValGlyTyrCysSerGlnIleProAsnCysAspMetSerHisGlyGln                               370375380                                                                      AspCysTyrArgGlyAsnGlyLysAsnTyrMetGlyAsnLeuSerGln                               385390395400                                                                   ThrArgSerGlyLeuThrCysSerMetTrpAspLysAsnMetGluAsp                               405410415                                                                      LeuHisArgHisIlePheTrpGluProAspAlaSerLysLeuAsnGlu                               420425430                                                                      AsnTyrCysArgAsnProAspAspAspAlaHisGlyProTrpCysTyr                               435440445                                                                      ThrGlyAsnProLeuIleProTrpAspTyrCysProIleSerArgCys                               450455460                                                                      GluGlyAspThrThrProThrIleValAsnLeuAspHisProValIle                               465470475480                                                                   SerCysAlaLysThrLysGlnLeuArgValValAsnGlyIleProThr                               485490495                                                                      ArgThrAsnIleGlyTrpMetValSerLeuArgTyrArgAsnLysHis                               500505510                                                                      IleCysGlyGlySerLeuIleLysGluSerTrpValLeuThrAlaArg                               515520525                                                                      GlnCysPheProSerArgAspLeuLysAspTyrGluAlaTrpLeuGly                               530535540                                                                      IleHisAspValHisGlyArgGlyAspGluLysCysLysGlnValLeu                               545550555560                                                                   AsnValAlaGlnLeuValTyrGlyProGluGlySerAspLeuValLeu                               565570575                                                                      MetLysLeuAlaArgProAlaValLeuAspAspPheValSerThrIle                               580585590                                                                      AspLeuProAsnTyrGlyCysThrIleProGluLysThrSerCysSer                               595600605                                                                      ValTyrGlyTrpGlyTyrThrGlyLeuIleAsnTyrAspGlyLeuLeu                               610615620                                                                      ArgValAlaHisLeuTyrIleMetGlyAsnGluLysCysSerGlnHis                               625630635640                                                                   HisArgGlyLysValThrLeuAsnGluSerGluIleCysAlaGlyAla                               645650655                                                                      GluLysIleGlySerGlyProCysGluGlyAspTyrGlyGlyProLeu                               660665670                                                                      ValCysGluGlnHisLysMetArgMetValLeuGlyValIleValPro                               675680685                                                                      GlyArgGlyCysAlaIleProAsnArgProGlyIlePheValArgVal                               690695700                                                                      AlaTyrTyrAlaLysTrpIleHisLysIleIleLeuThrTyrLysVal                               705710715720                                                                   ProGlnSer                                                                      (2) INFORMATION FOR SEQ ID NO:4:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 2288 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: cDNA                                                       (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                        TAGGCACTGACTCCGAACAGGATTCTTTCACCCAGGCATCTCCTCCAGAGGGATCCGCCA60                 GCCCGTCCAGCAGCACCATGTGGGTGACCAAACTCCTGCCAGCCCTGCTGCTGCAGCATG120                TCCTCCTGCATCTCCTCCTGCTCCCCATCGCCATCCCCTATGCAGAGGGACAAAGGAAAA180                GAAGAAATACAATTCATGAATTCAAAAAATCAGCAAAGACTACCCTAATCAAAAAGATCC240                AGCACTGAAGATAAAAACCAAAAAAGTGAATACTGCAGACCAATGTGCTAATAGATGTAC300                TAGGAATAAAGGACTTCCATTCACTTGCAAGGCTTTTGTTTTTGATAAAGCAAGAAAACA360                ATGCCTCTGGTTCCCCTTCAATAGCATGTCAAGTGGAGTGAAAAAAGAATTTGGCCATGA420                ATTTGACCTCTATGAAAACAAAGACTACATTAGAAACTGCATCATTGGTAAAGGACGCAG480                CTACAAGGGAACAGTATCTATCACTAAGAGTGGCATCAAATGTCAGCCCTGGAGTTCCAT540                GATACCACACGAACACAGCTATCGGGGTAAAGACCTACAGGAAAACTACTGTCGAAATCC600                TCGAGGGGAAGAAGGGGGACCCTGGTGTTTCACAAGCAATCCAGAGGTACGCTACGAAGT660                CTGTGACATTCCTCAGTGTTCAGAAGTTGAATGCATGACCTGCAATGGGGAGAGTTATCG720                AGGTCTCATGGATCATACAGAATCAGGCAAGATTTGTCAGCGCTGGGATCATCAGACACC780                ACACCGGCACAAATTCTTGCCTGAAAGATATCCCGACAAGGGCTTTGATGATAATTATTG840                CCGCAATCCCGATGGCCAGCCGAGGCCATGGTGCTATACTCTTGACCCTCACACCCGCTG900                GGAGTACTGTGCAATTAAAACATGCGCTGACAATACTATGAATGACACTGATGTTCCTTT960                GGAAACAACTGAATGCATCCAAGGTCAAGGAGAAGGCTACAGGGGCACTGTCAATACCAT1020               TTGGAATGGAATTCCATGTCAGCGTTGGGATTCTCAGTATCCTCACGAGCATGACATGAC1080               TCCTGAAAATTTCAAGTGCAAGGACCTACGAGAAAATTACTGCCGAAATCCAGATGGGTC1140               TGAATCACCCTGGTGTTTTACCACTGATCCAAACATCCGAGTTGGCTACTGCTCCCAAAT1200               TCCAAACTGTGATATGTCACATGGACAAGATTGTTATCGTGGGAATGGCAAAAATTATAT1260               GGGCAACTTATCCCAAACAAGATCTGGACTAACATGTTCAATGTGGGACAAGAACATGGA1320               AGACTTACATCGTCATATCTTCTGGGAACCAGATGCAAGTAAGCTGAATGAGAATTACTG1380               CCGAAATCCAGATGATGATGCTCATGGACCCTGGTGCTACACGGGAAATCCACTCATTCC1440               TTGGGATTATTGCCCTATTTCTCGTTGTGAAGGTGATACCACACCTACAATAGTCAATTT1500               AGACCATCCCGTAATATCTTGTGCCAAAACGAAACAATTGCGAGTTGTAAATGGGATTCC1560               AACACGAACAAACATAGGATGGATGGTTAGTTTGAGATACAGAAATAAACATATCTGCGG1620               AGGATCATTGATAAAGGAGAGTTGGGTTCTTACTGCACGACAGTGTTTCCCTTCTCGAGA1680               CTTGAAAGATTATGAAGCTTGGCTTGGAATTCATGATGTCCACGGAAGAGGAGATGAGAA1740               ATGCAAACAGGTTCTCAATGTTTCCCAGCTGGTATATGGCCCTGAAGGATCAGATCTGGT1800               TTTAATGAAGCTTGCCAGGCCTGCTGTCCTGGATGATTTTGTTAGTACGATTGATTTACC1860               TAATTATGGATGCACAATTCCTGAAAAGACCAGTTGCAGTGTTTATGGCTGGGGCTACAC1920               TGGATTGATCAACTATGATGGCCTATTACGAGTGGCACATCTCTATATAATGGGAAATGA1980               GAAATGCAGCCAGCATCATCGAGGGAAGGTGACTCTGAATGAGTCTGAAATATGTGCTGG2040               GGCTGAAAAGATTGGATCAGGACCATGTGAGGGGGATTATGGTGGCCCACTTGTTTGTGA2100               GCAACATAAAATGAGAATGGTTCTTGGTGTCATTGTTCCTGGTCGTGGATGTGCCATTCC2160               AAATCGTGCTGGTATTTTTGTCCGAGTCGCATATTATGCAAAATGGATACACAAAATTAT2220               TTTAACATATAAGGTACCACAGTCATAGCTGAAGTAAGTGTGTCTGAAGCACCCACCAAT2280               ACAACTGT2288                                                                   (2) INFORMATION FOR SEQ ID NO:5:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 19 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:                                        TCAGTGTCCTGCATAGTAT19                                                          (2) INFORMATION FOR SEQ ID NO:6:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 27 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:                                        CCAGATCTTGTTTGAGCTAAGTTGCCC27                                                  (2) INFORMATION FOR SEQ ID NO:7:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 21 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:                                        GCTGGGATCATCAGACACCAC21                                                        (2) INFORMATION FOR SEQ ID NO:8:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 25 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:                                        ATACCAGCTGGGCAACATTGAGAAC25                                                    (2) INFORMATION FOR SEQ ID NO:9:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 26 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:                                        GGCAACTTATCCCAAACAAGATCTGG26                                                   (2) INFORMATION FOR SEQ ID NO:10:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 25 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10:                                       ACTCTGAATGAGGCTGAAATATGTG25                                                    (2) INFORMATION FOR SEQ ID NO:11:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 32 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11:                                       GGCATGCACAGTTGTATTGGTGGGTGCTTCAG32                                             (2) INFORMATION FOR SEQ ID NO:12:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 25 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12:                                       CACATATTTCAGCCTCATTCAGAGT25                                                    (2) INFORMATION FOR SEQ ID NO:13:                                              (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 23 base pairs                                                      (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: other nucleic acid                                         (A) DESCRIPTION: /desc = "OLIGONUCLEOTIDE"                                     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13:                                       AACAGGTTCTCAATGTTTCCCAG23                                                      __________________________________________________________________________ 

We claim:
 1. A modified TCF comprising TCF having a deletion of one or more oligosaccharide chains, said modified TCF having an amino acid sequence wherein at least one of the amino acid residues responsible for binding N-linked oligosaccharide chains is modified such that at least one of the N-linked oligosaccharide chains is prevented from binding to the modified TCF, wherein the amino acid residues responsible for binding the N-linked oligosaccharide chains are selected from the group consisting of asparagine, threonine and serine.
 2. The modified TCF of claim 1 wherein the amino acid sequence is Sequence ID No. 2 or Sequence ID No.
 3. 3. The modified TCF of claim 1 wherein at least one of the amino acid residues responsible for binding N-linked oligosaccharide chains is replaced such that at least one of said chains is prevented from binding to at least one Asn residue in Sequence ID No.
 1. 4. The modified TCF of claim 3 wherein the Asn residue is selected from the group consisting of: Asn residue at position 289, 397, 561, and 648 in Sequence ID No.
 1. 5. The modified TCF of claim 1 wherein Ala is the amino acid residue at position 563 as depicted in Sequence ID No.
 2. 6. The modified TCF of claim 1 wherein Gln is the amino acid residue at position 289 and Ala is the amino acid residue at position 563 as depicted in Sequence ID No.
 3. 7. A modified TCF produced by expression of a DNA encoding the amino acid sequence of Sequence ID No.
 2. 8. A modified TCF produced by expression of DNA encoding the amino acid sequence of Sequence ID No.
 3. 9. A DNA sequence encoding modified TCF having a deletion of one or more oligosaccharide chains, said DNA sequence comprising a nucleic acid sequence encoding an amino acid sequence wherein at least one of the amino acid residues responsible for binding N-linked oligosaccharide chains is modified such that at least one of the N-linked oligosaccharide chains is prevented from binding to the modified TCF, wherein the amino acid residues responsible for binding the N-linked oligosaccharide chains are selected from the group consisting of asparagine, threonine and serine.
 10. The DNA sequence of claim 9 wherein the amino acid sequence is Sequence ID No. 2 or Sequence I.D. No.
 3. 11. The DNA sequence of claim 9 wherein the nucleic acid sequence encoding the amino acid sequence responsible for binding N-linked oligosaccharides chains is modified such that at least one of said chains is prevented from binding to at least one Asn residue in the amino acid sequence encoded by Sequence I.D. No.
 4. 